I have thousands of old datecode PCBs which has an Entek and HASL finished. Entek PCBs are about 6 � 1.5 years old and HASL boards are at 1 - 2 years old. To make it worse, some of them came in the loose form, no vacuum seal� nothin�.

As for the HASL not much of the worry compared to the ENTEK. My boss has suggested me to send all my board for re-entek. Fine to me except for those plated thru� hole, in the case on thru� hole oxidised, can the re-entek process cater/reach the barrel ? My wild suggestion was get them stripped/HASLed as there is no fine pitch on the board.

Can someone pls explain how does the re-Entek process caried out? Can this Entek finished board be stripped and converts to HASL? What would you do if you were in my shoe ? It is too pain for the company to scrap these board as they are very expensive and the quantity if too high i.e. total = a mix of 15,000 diff. type of PCB.

Sounds kwazy that you�d end-up with that volume of old boards, but it�s probably one of those deals where correcting the problem keeps getting put off and keeps getting put off, until it gets smelling SO bad!!! Er, did the fine person that gave you those lousy 0402 dump these boards on you also? [What the hey, let�s blame it on �em anywho.]

We have never re-Entek�d our boards. [�Bout 5 er 6 years ago our lazy behind, good fer nuthin buyer was getting BIG bonuses because she was lowering the cost of bought in parts by volume buying. Unfortunately, all this buying has little to do with the build plan or customer demand. So the production manager got fired, because he couldn't hit cost bogies when trying to economically solder these nasty boards that had been sitting around on the shelf for a cuppla years, humm.] After we figured-out what was happening, we started buying in littie bittie batches when we ship littie bittie volume of products. [And the buyer got another bonus for lying that she figuring that out too!!! Some people just think with the wrong head. I don�t get it!!!]

If I had yer Entek boards, I�d make-up a special stencil for each part number, reflow the pups with the hi-test flux, contract wash �em, test for cleanliness, bake �em, bag �em, and clean-up the messes on the bench, when that day came.

You�re correct the degraded Entek will crater your through holes. This begs the side question: Has the copper plating been damaged enough to compromise the reliability of the product? [Ummm, probably not. Although my concern about this would increase with the wimpiness of the flux I expected to be using when I worked through this inventory backlog.]

That aside, it�s fairly easy to strip Entek with alcohol, but howdya know that ya removed all of the Entek? Dunno.

On the other hand, Entek is applied by dipping or spraying and it wouldn�t surprise me if the re-coating process didn�t strip the old the coating. BUT, none of that Entek re-processing does anything to remove the underlying corrosion of the copper surface that must be removed prior to applying a new solderability protection, be it OSP or HASL. [Kinda like that brass lamp on your front stoop, beside the front door. It�s been lacquer coated, but still corrodes because the porosity of the coating allows moisture in the air to pass to the metal.]

Given the volume of inventory you have to build-down, yer likely looking at something with greater shelf longevity than OSP. There�s no reason why you can�t HASL your Entek boards. Issues are: 1 Board layout 2 Getting the job done.

GETTING THE JOB DONE. Your fabricator will probably tell you how tough it is going to be to do the job. Hey, it�s not like we�re taking pictures of worms hanging-out by the vents in the Marianis Trench. Or digging-up the streets of Boston for 10 years and blowing the original $3-billion dollar budget: now approaching 12 or 15, on the way to 20-billion dollars. [Then again, liberals are always looking for new ways to take money from people.] Your fabricator could have issues with the fixturing of your boards to match-up with their processes. [Continuing with that thought, your fabricator may not be the proper shop for the job. A specialist may be in order.]

Oooo, let me get a side issue on the table, before I forget. There is no reason not to expect that these boards haven�t been sopping-up moisture, like a Redbone at a bigo puddle on a July after noon. So beyond your primary concern of restoring solderability, there should be the concern of moisture venting from the boards during soldering process.

Thanx Dave, I agree with you on the planning part...yapp!! the same guy who've thrown an old datecode components to me..now they did it again on the PCB.

Well Dave, could you explain a little bit more about the "hi-test flux" that you mentioned above. Can I used the paste flux ? i.e. the one we used for Sipad Technology from Promosol and reflow them ( I guess I have to print on the via or plated through hole as well ). About the Contract wash..will the DI water ( Aqueos ) cleaning be sufficent ?

Thanx Dave, I agree with you on the planning part...yapp!! the same guy who've thrown an old datecode components to me..now they did it again on the PCB.

Well Dave, could you explain a little bit more about the "hi-test flux" that you mentioned above. Can I used the paste flux ? i.e. the one we used for Sipad Technology from Promosol and reflow them ( I guess I have to print on the via or plated through hole as well ). About the Contract wash..will the DI water ( Aqueos ) cleaning be sufficent ?

We can offer two ways. We have a process control tool for OSP boards to validate the finish......but the dates yer talking may be best to take Daves F suggestion.

NOW as far as the HASL finish goes...We may have your answer. We can Chemically reverse the oxidation process and make the boards like new (ROSA process). With this we need to know Board dimensions, make up, quantity, and HASL finish.

I had forgotten that it was you that was on the Sipad adventure. [But then again, who can keep track of yer aliases? ;-)] You just go from one adventure to the next.

Expanding On Dave�s Hi-Test Flux Method Theory �

PASTE: Yes, contact your favorite paste sales person and ask them for a solder paste with their highest activity electronic grade flux. As you say it�ll probably be a water soluble with parental advisory labels. Probably the one you used in the Sipad adventure will be fine.

STENCIL: Yes, you need print on the via, plated through hole, test pad, grounding pad, etc. as well as pads and PTH donuts. When you do this, consider overprinting all surface features, just to be sure your left with no OSP ghosts.

Obviously, this is going to take some putzing to get the proper amount of paste. Consider laying the paste on thick to provide protection during the upcoming years of storage. Obviously, not so thick that you fill the through holes. Similarly, it would be better if you just coated the via walls and didn�t fill the vias, but filled vias may just end-up being one of those things that happen.

REFLOW PROFILE: Pretty standard stuff. Certainly, you�d prefer to do this in one pass [and not have to paste and reflow the second side]. So, first the flux needs time to get from top to bottom of the PTH, then the solder needs to have time and heat to cover the course. But you can�t leave the board at liquidous too long, because that�ll bulk-up the intermetallics. Finally, a steep cooling ramp will produce a fine grain that will last longer.

CLEANING: Sure, no reason to think your aqueous cleaner wouldn�t be fine. ["Contract cleaner" was for any NC-type that might shy away from doing this because of cleaning issues.]